The present invention relates to a driving apparatus for an electric vehicle and, particularly, to a technique effectively applied to the driving apparatus for an electric vehicle, which is driven by a plurality of power sources.
An electric vehicle includes a battery accumulating power and a motor driving driving-wheels, and can travel by the power from the charged battery. The electric vehicle has advantages of emitting no exhaust fumes during a vehicle run, having good energy efficiency, and the like while it has the problems that mileage per charge is short and charging time for the battery is long and a troublesome charging work is required.
To solve these problems, a so-called hybrid vehicle has been developed as an electric vehicle equipped with an internal combustion such as a gasoline engine, an diesel engine, or the like in addition to a motor. In driving systems of the hybrid vehicles, there are a series type, a parallel type, and a series-parallel type. The electric vehicle of a series type is such that the battery is charged up to a value of power generated through an electric generator driven by an engine and the vehicle is driven by a motor. Since the engine is used to generate electric power, it can be used through only an efficient revolution speed (for example, see Japanese Patent Laid-open (TOKUKAIHEI) No. 10-285708). The electric vehicle of a parallel type is such that an engine is mainly used as a drive source for a vehicle run and drive power is assisted by the motor at the time of start and/or acceleration at which the vehicle takes loads. When the vehicle takes light loads due to bad engine efficiency, a function of the motor is changed to an electric generator to charge the battery.
Meanwhile, the electric vehicle of a series-parallel type has an electric generator in addition to an engine and a motor. The drive of the vehicle is changed to any one of drive by the engine, drive by the motor, and drive by both drive sources depending on running states, thereby allowing the engine and motor to be used under the efficient conditions. In the electric vehicle having the driving system, the motor is used to drive the vehicle at the time of start at which drive torque is required, and the vehicle is driven by the engine when its speed is increased, and the vehicle is driven by the motor and engine at the time of a uphill run at which it takes heavy loads, and electric power is generated during the vehicle run when the engine takes light load (for example, see Japanese Patent Laid-open (TOKUKAIHEI) No. 9-226393).